Air Pollution: Mining's Dark Clouds And Their Causes

Mining is considered one of the main sources of pollution in the world. It is one of the most critical sectors that constitute a significant portion of the global economy. However, due to the nature of its production stage, mining causes environmental problems, with air pollution being one of the leading causes of environmental health issues globally. Both above-ground and underground mining processes produce air pollution and can generate harmful aerosols, including particulate matter, arsenic, and diesel. One primary source of mining air pollution comes from mineral extraction, including the processes of excavation, blasting, transportation of materials, and wind erosion.

Metal mining releases toxins, including arsenic and mercury

Metal mining is one of the biggest sources of air pollution globally. The smelting of metals, including gold, is a primary source of arsenic emissions and other toxins. During the smelting process, ore is subjected to very high temperatures to melt the metal and release it from other materials in the ore. While smelting technology has improved over the past 50 years, the process still releases a significant amount of toxins, including arsenic and mercury.

Mercury is a potent neurotoxin, and exposure can result in illnesses ranging from impaired vision and muscle weakness to permanent kidney and nerve damage, depending on the level and duration of exposure. Low-dose exposure is a subtle threat that may go unnoticed until diagnosed by its complications, such as fatigue, anxiety, and detrimental impacts on intelligence quotient (IQ) and intellectual function in children. Regular alcohol consumption combined with high blood mercury concentrations can lead to oxidative stress, impairment of cellular metabolism, and cell death due to liver damage.

Arsenic is a known carcinogen, and exposure can occur through inhalation, ingestion, dermal contact, and the parenteral route. Arsenic is present at low concentrations in virtually all environmental matrices, and its concentration in air ranges from 1 to 3 ng/m3 in remote locations, increasing to 20-100 ng/m3 in cities.

Both arsenic and mercury are considered systemic toxicants that can induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens. Heavy metal toxicity can disrupt cellular events, including growth, proliferation, differentiation, damage-repairing processes, and apoptosis.

Coal mining generates dust and pollutants from uncovered coal stockpiles

Coal mining is a major source of air pollution, and it harms public health. One of the ways in which coal mining generates air pollution is through uncovered coal stockpiles. When wind blows over these uncovered coal piles, it results in fugitive coal dust emissions, which are a source of PM2.5. PM2.5 refers to fine particulate pollution, which are particles less than 2.5 micrometers in diameter and about 30 times thinner than a strand of hair. These particles can be carried over 25 miles from the source and inhaled by pedestrians, causing serious health issues.

In addition to wind erosion, coal oxidation also contributes to air pollution. The oxidation of coal and gangue (mining waste products) leads to the formation of pollutants. Furthermore, the handling of coal, which includes processes such as moving it from the mine mouth to stockpiles, crushing it, and loading it for delivery, creates additional pollution. These activities generate fine particulates that can have detrimental effects on human health.

To mitigate the impact of coal mining on air quality, various technologies and practices for dust suppression can be employed. For instance, fixed sprinklers can be installed at coal handling plants and along transportation roads. Mobile water sprinklers can also be utilized on major roads to reduce dust stirring. Covering coal-transporting trucks with tarps is another recommended practice to prevent coal spillage during transportation.

Real-time air quality monitoring is crucial to understanding pollution exposure levels and protecting workers, nearby communities, and the environment. By monitoring air quality, regulatory guidelines can be enforced, and appropriate actions can be taken to reduce pollution levels and improve visibility. Additionally, dust suppression techniques can be more effectively implemented with accurate data on pollution levels.

Blasting and excavation release harmful gases and particulate matter

Blasting and excavation are integral parts of the mining process. Drilling and blasting involve drilling a hole into a rock, partially filling it with explosives, stemming the hole with inert material, and finally detonating the explosive to cause the rock to collapse. This is a highly effective method for breaking rocks for excavation, especially in the case of hard rocks where digging is not possible. However, the use of explosives and the collapse of rocks can release harmful gases and particulate matter into the air, contributing to air pollution.

The type of explosive used depends on the hardness of the rock. Harder rocks require higher velocity explosives to shatter and break them, while softer rocks use low-velocity explosives to generate more gas pressure and a greater heaving effect. The choice of explosive is crucial, as it directly impacts the amount and type of particulate matter released. For instance, black powder produces effects similar to those of a wedge, while dynamite is more akin to a hammer.

Rock blasting releases harmful particulate matter into the air, which can have adverse health effects on miners and nearby communities. Particulate matter refers to tiny solid and liquid particles suspended in the air, which can be inhaled and cause respiratory issues and other health problems. Additionally, the use of explosives can release toxic gases, such as mercury and arsenic, which are dangerous to humans and the environment. Mercury exposure can lead to impaired vision, muscle weakness, and permanent kidney and nerve damage. Arsenic, a known carcinogen, is another toxic substance released during the blasting process.

To mitigate the release of harmful gases and particulate matter, several measures can be implemented. Blasting mats can be used to contain the blast, suppress dust, and prevent fly rock. Additionally, dust suppression techniques, such as surface miners, mist sprayers, and wet drilling, can be employed to reduce dust generation. Regular vehicle maintenance is also crucial, as vehicles and heavy equipment used in mining produce exhaust emissions that contribute to pollution levels. Real-time air quality monitoring is essential to detect spikes in air pollution and protect workers and nearby communities.

Diesel vehicles and heavy equipment produce exhaust emissions

To address these issues, various technologies and practices have been developed to reduce diesel emissions. The Diesel Emissions Reduction Act (DERA) was established to promote diesel emission reduction projects, with grants and rebates provided to encourage the adoption of cleaner technologies. Engine modifications, electronic-controlled fuel injection systems, and improved fuel properties have been explored, but the desired emission levels have not been achieved solely through these measures. As a result, the focus has shifted to implementing aftertreatment emission control systems, which can eliminate pollutants from the exhaust before they are released into the atmosphere.

Exhaust gas recirculation (EGR), lean NOx trap (LNT), and SCR technologies have been the most studied methods for reducing NOx emissions. EGR systems recirculate exhaust gas back into the combustion chamber, reducing the formation of NOx by lowering the combustion temperature. However, EGR alone cannot meet the current emission standards for heavy-duty vehicles. Therefore, a combination of these technologies and the continued development of zero-emission vehicles (ZEVs) are crucial for improving air quality in mining and reducing the health and environmental risks associated with diesel exhaust emissions.

Regulatory certainty and strong regulations are also essential to encourage private investment in ZEV infrastructure. Manufacturers are already making progress, with companies like Mercedes, Nikola, and Ford announcing new long-haul electric and fuel cell electric vehicles. These advancements provide viable alternatives to diesel trucks, offering similar cargo capacities and refuelling times while reducing emissions. By transitioning to ZEVs, the heavy-duty trucking industry can significantly reduce air pollution, improve public health, and contribute to the fight against climate change.

To summarise, diesel vehicles and heavy equipment used in mining contribute significantly to air pollution through their exhaust emissions. Addressing this issue requires a combination of regulatory measures, technological advancements, and the adoption of zero-emission alternatives. By prioritising the reduction of diesel exhaust emissions, we can mitigate the adverse effects on human health and the environment, ensuring cleaner air for miners, nearby communities, and the planet.

Abandoned mines can cause nonpoint source pollution and acidification of water bodies

Abandoned mines can have a detrimental impact on the environment, causing nonpoint source pollution and leading to the acidification of water bodies. Nonpoint source pollution refers to the diffuse contamination of water or air that does not originate from a single discrete source. In the context of abandoned mines, this type of pollution is often associated with runoff from mining operations, particularly in the absence of proper reclamation practices.

One significant consequence of abandoned mines is the occurrence of acid mine drainage, which is prevalent in areas with a history of coal mining. Acid mine drainage occurs when surface water or shallow subsurface water reacts chemically with rocks containing sulfur-bearing minerals, resulting in the formation of sulfuric acid. This highly acidic water, rich in heavy metals, can contaminate nearby water bodies, altering their pH levels and causing ecological damage.

Another issue with abandoned mines is the exposure of rocks that can undergo chemical reactions with air and water, leading to the creation of acidic runoff. This acidic water can seep into nearby water bodies, further contributing to nonpoint source pollution. The lack of proper management and reclamation of the mining site increases the risk of soil erosion and the release of contaminants into the surrounding environment.

The impact of abandoned mines on water bodies can be complex and challenging to address. The pollution is often the result of multiple sources and activities, making it difficult to regulate and control. It is not limited to a single location but can affect a large area, including rivers, lakes, and seas. The pollutants can include heavy metals, toxic contaminants, chemicals, and nutrients, all of which have detrimental effects on aquatic life and the surrounding ecosystem.

To mitigate the environmental impact of abandoned mines, proper reclamation and restoration practices are essential. This includes efforts to prevent soil erosion, control water runoff, and neutralize or contain acidic water before it enters nearby water bodies. Additionally, regular monitoring of water quality in areas affected by abandoned mines is crucial to detect and address any changes in water chemistry, protecting both the environment and the health of surrounding communities.

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